U.S. Pat. No. 5,590,442 describes web storage apparatus for non-woven fabrics. The web storage apparatus is located between a web producer and web processing apparatus, e.g., between a carding machine, operating at constant output speed, and fabric laying apparatus, operating at rhythmically variable take-up speeds. In such fabric laying apparatus, the transport speed of the web within the machine changes during transport depending on the movements of the laying carriage within the fabric laying apparatus. The web storage apparatus is controlled in accordance with the transport speed of the laying belts of the fabric laying apparatus, such transport speed fluctuating with the rhythm of the absolute traveling speed of the laying carriage.
This known web storage apparatus consists of a U-shaped section of variable length of an endless belt conveyor extending between the web producer and the fabric laying apparatus. The web storage apparatus supplies the web output from the web producer, which produces web material at a substantially constant speed, to the fabric laying apparatus, which requires web material to be supplied to it at a fluctuating speed. The length of the U-shaped section (and thereby the length of the path that web material must travel) is varied by displacing a frame which holds a pair of deflecting rollers. A carriage-mounted endless support belt aligns with the conveyor belt in its U-shaped section, and in this section, the support belt tightly contacts the conveyor belt, thereby clamping the web material between these two belts. The web storage apparatus is therefore capable of controlling the regular web supply speed of the web producer in accordance with the variable take-up speed of the web processing apparatus.
In order to accomplish the changes in the path length, also known as web buffering, the movements of the frame and the carriage must be matched with one another, which requires special effort, since a sufficient tension of the conveyor belt must always be ensured to maintain the clamping effect between the conveyor belt and the support belt in order to prevent any damage of the sensitive, unsolidified web material in the web storage apparatus. Such coordinated control is both complex and costly. Further, along some portions of the web path from the infeed from the web producer to the outfeed to the web processing apparatus, the web material is not fully clamped, leaving the web material susceptible to disturbances from drafts. Thus there is a need for web buffering apparatus which can provide the web speed-matching function between various pieces of equipment in less costly, less complex manner and provide protection for the web while maintaining a high quality level in the web material.